Spinning artificial filaments



Patented June 15, 1954 2,681,265 SPINNING ARTIFICIAL FILAMENTS Howard M.Hoxie, Cheste ican Viscose Corporation, corporation of Delaware r, Pa.,assignor to Amer- Wilmington, DeL, a

N Drawing. Application November 27, 1948, Serial No. 62,413

8 Claims.

This invention relates to the production of synthetic filaments or yarnscomprising acrylonitrile polymers.

The patent literature contains statements to the effect thatacrylonitrile polymers containing at least 85% by weight acrylonitrilein the polymer molecule can be formed into synthetic filaments or yarnsby extruding a dimethyl formamide solution of the polymer into water ata temperature of 70 C., and stretching the filaments or yarns thusobtained to 6.3 times their original length.

In actual practice, it has been found to be impossible to obtain usefulfilaments or yarns by spinning the dimethyl formamide solutions into abath consisting of water, regardless of variations in such factors asimmersion length, bath temperature, spinning speed, jet design, orfilament size. The filaments obtained by spinning the solutions into abath consisting of water are extremely weak, fragile, and brittle, andare practicaly inextensible. Such filaments or yarns pletely coagulated,lated areas occuring, generally, at the surfaceof the filament, whichthus comprises a layer of coagulated polymer surrounding a plastic core.Evidently, this condition of the filaments obtained by spinning thedimethyl formamide solutions into a bath consisting of water is due todifierences between the rate of difiusion (or extraction) of thedimethyl formamide from the interior of the fiber outwardly, and therate of diffusion of the coagulating liquid inwardly, whereby diffusionof the spinning solvent out of the fiber is prevented or hampered by thecoagulated layer formed initially at the surface of the filament.Whatever may be the explanation of the diificulty, it is a fact thatwhen the solutions water, the filaments withdrawn from the bath are notcapable of accepting sufficient stretch to efiect appreciable molecularit has been necessary to employ organic solvents such as isopropanol,glycerol, or aqueous salt solutions, such as aqueous solutions ofcalcium chloride, as the coagulating liquid. All such liquids entailtroublesome problems of coagulating bath regeneration and solventrecovery.

It is, therefore, an object of this invention to provide a new method ofproducing filaments and yarns from solutions of the acrylonitrilepolymers in dimethyl formamide by a wet spinning procedure, wherebyhomogeneous filaments given a stretch of from 200 to 300%. meritswithdrawn from the bath are coagulated so that they possess sufiicientplasticity to permit extension thereof under stretching, withoutrupture. It is known that stretching of the acrylonitrile polymerfilaments efiects an improvement in the physical properties such astenacity and resilience. While it has been stated in the patentliterature that acrylonitrile polymer yarns produced by wet spinning adimethyl iormamide solution of the polymer can be stretched at any theusual after the filaments have been withdrawn from the coaguwashing toremove the remaining solvent. The filaments produced by the presentmethod are generally stretched by 200 to 300% after they are withdrawnfrom the dimethyl formamide-water spinning bath prior to washingthereof. This stretching can be accomplished at room temperature bypassing the in dimethyl formamide and spun into a coagulating bathconsisting of a water-dimethyl formamide mixture containing from 35 tovolume per cent of dimethyl formamide in accordance Alternately, whilethe I introduced as dope 3 the group C'=C such as for example, 2-vinylpyridine, vinyl acetate, vinyl chloride, acrylic acid and its esters,styrene, isobutene, and butadiene, as well as other vinyl and acryliccom-- pounds, and other olefin or diolefin hydrocarbons. The coagulatingbaths of the present invention are particularly useful in the spinningof dimethyl formamide solutions of acrylonitrile polymers containing atleast 65% by weight acrylonitrile in the polymer molecule and having amolecular weight of 15,000 to 250,000 as determined by specificviscosity data using the standinger equation, since those polymers aresuitable for the production of filaments and yarns which may be used forgeneral textile purposes.

The advantages of the method of this invention are numerous andimportant. Spinning can be performed at room temperature, thuseliminating the need for means for heating the bath. Once the spinningoperation has been initiated the only expedient required in order tomaintain the composition of the spinning bath constant is the periodicalor continuous addition of the calculated amounts of plain water, so thatexpensive bath recirculating and regenerating systems are entirelyavoided. In addition, the solvent recovery procedure is simple since inorder to recover the solvent, it is only necessary to distill ofi thewater, which can be accomplished rapidly and at comparatively littleexing bath consisting of 30% The acrylonitrile polymers which are formedinto filaments or yarns in accordance with the invention may be producedby any suitable polymerization procedure, e. g., by emulsion,suspension, bulk, or solution polymerization procedures.

The following examples are illustrative of preferred methods ofpracticing the invention, although the invention is not to be limited bythe details set forth therein.

Example I 13% dimethyl formamide solution of a copolymer which wasprepared by the solution copoiymerization of acrylonitrile and 2-viny1pyridine and which contained 15% of 2-vinyl pyridine by weight in thepolymer molecule was extruded through a spinneret having 44 holes eachhaving a diameter of 4 mils into a coagulatwater and 70% dimethylformamide, by volume, at 23 C. After a bath travel of 9.5 inches, at aspeed of 260 inches/min. the yarn was withdrawn from the bath andstretched 220% between two pairs of canted godets. The yarn was thenwashed with water, collected, and dried in air. It had a dry tenacity of1.3 gms. per denier; dry extensibility, 25%. The yarn was then stretched350% by passing it through a tube heated to 175 C. at a speed of 70it./min. The resulting yarn had the following characteristics:

Tensile Filaments Denier Strength, 7 figfl gins/denier p H BeforeReiaxationnu 44 54 4.9 8 After Relaxation in Boiling Water 44 62 4. 2 20pense. Further advantages are that the coagulating bath isnon-inflammable, non-volatile, and relatively non-toxic.

In the practice of this invention, the concentration of dimethyliormamide in the bath must be maintained at from to 80% by volumethroughout the entire spinning operation.

This requires 'the addition of only small amounts of water. In the caseof other spinning baths, for example, glycerol, the presence of morethan a small amount, not over 20%, of dimethyl formamide is detrimentaland results in breaking of the filaments at the jet and excessively weakyarns. In order to keep the concentration of dimethyl formamideintroduced during spinning into a glycerol precipitating bath at orbelow the comparatively low critical value for satisfactory spinning, itis necessary to add. substantial amounts of the expensive glycerol tothe bath. Thus, for each liter of dimethyl formamide pumped into thebath as dope, it is necessary to add four liters of glycerol in order toprevent increase in the dimethyl formamide concentration above 20%. Incontrast to this, when the spinning bath comprises a mixture of, say,67% dimethyl formamide and 33% water, amounts of dimethyl formamidegreater than are do not have to be added, and it is necessary to addonly a liter of water to the bath, for each liter of dimethyl formamidepumped in as dope, in order to maintain the necessary bath composition.

The filaments or yarns obtained by the present method compare favorablywith, and in many cases are superior to, the yarns which can be obtainedby spinning the solutions of the acrylonitrile polymers into organicsolvents such as glycerol, or into salt solutions.

The tenacity and extensibility of the final heatstretched yarn areessentially the same as those of a yarn obtained by spinning thedimethyl formamide solution into glycerol or calcium chloride solution,at elevated temperatures, in spite of the fact that, prior to the finalheating and stretching step, the tensile strength of the yarn wassomewhat lower than thatv of yarns obtained when organic solvents orsalt solutions were used to effect the coagulation. The yarn produced bythe present method exhibits excellent stability at high temperature, isnot cemented, and can be dyed by means of wool dyes of the strong acidtype, such as Wool Fast Scarlet. The yarn is substantially free fromvoids when examined under a microscope which magnifies the cross section500 times.

Example II A 15 solution of polyacrylonitrile in dimethyl formamide wasextruded through a O-holeB-mil jet into a bath comprising 32% water and68% dimethyl formamide by volume. After an immersion of five inches(speed- 260 in./min.) the yarn was withdrawn..from the bath, stretched200%, washed in water, and dried.

.This yarn had a tensile strength of 1.2 g./d. and an extensibility of24%. 300% stretch was applied to the yarn duringits passage through atube heated to C. The tenacity of. the heat-stretched yarn was i5ms/denier. After relaxation in boiling water the tenacity was 3.82gms./denier, the extensibility 13%, and the denier 74.

v I Example HI A copolymer containing 17% acrylamide and 83%acrylonitrile by weight was prepared by water solution polymerization.:A 12% solution Of this p l m in dim thyl formamide w s X- 2. A methodas in claim 1, wherein the coagutruded through a 9o-hole 3-mil jet intoa bath lating bath consists of a mixture of water and comprising waterand 45% dimethyl by volume of dimethyl formamide. formamide, After animmersion of three inches 3. A method as in claim 1, wherein the acry-(speed=2-60 iii/mind the yarn was withdrawn 5 lonitrile polymer is aoopolymer of acrylonitrile from the bath, stretched 200%, washed, andand 2-viny1 pyridine containing by weight dried. The yarn so obtainedhad a tenacity of of acrylonitrile in the polymer molecule.

1.42 gins/denier and extensibility of 28.3%. 4. A method as in claim 1,wherein the acry- Passage through a tube heated to 180 0. perlonitl'ilepo ymer is polyacrylom'trile.

mitted application of 400% stretch and pr0- 1o 5.A method as in claim 1,wherein the acryduced a yarn of denier which had a tenacity l nitrilepolymer is a copolymer of acrylonitrile of 5.1 gms/denier and anextensibility of 8%. d ylamid containing y W ht 1 Since it is obviousthat some changes and mociiaclylfiniblile n he P y moleculefications canbe made in the above described A method as n claim wherein the pndetails without departing from the nature and 5 g is performed at roomtemperature. spirit of the invention, it is to be understood that Amethod as in Claim wherein the ythe invention is not to be limitedthereto exce t lonitrile p lym r is a p lym r of acryl nitrile asdefined in th appended claims and vinyl acetate containing at least 65%by I l weight of acrylonitrile in the polymer molecule. 1. A method forthe production 01 yarns from 0 A method as in 0391111 1, wherein the aya solution of a fiber-forming acrylonitrile polylollitlilo P ymer is aoopolymer of acrylonitrile mgr containing in th pglymer molecule, atleast and an acrylic acid ester containing at least 65% 65 ofacrylonitrile in dimethyl formamide whi h by weight of acrylonitrile inthe polymer molecule. comprises spinning the solutions into a coagu-Peferences Cited in the 1 f lating bath consisting essentially of amixture of O fi e 0 thls patent Water and from 35 to 80% by volume ofdimethyl UNITED STATES PATENTS formamide, withdrawing the yarn thusformed Numbe Name Date from the bath, and stretching the yarn by 2002,236,061 zard Mar. 25, 1941 to 300% of its length, the composition ofthe 2,360,405 r yfus Oct. 17, 1944 coagulating bath being maintainedsubstan- 0 2,404,714 a ham July 23, 1946 tially constant from thebeginning to the end 2,404,723 Memer July 23, 1946 of the spinningoperation. 2,420,565 Rugeley et a1. May 13, 1947

1. A METHOD FOR THE PRODUCTION OF YARNS FROM A SOLUTION OF AFIBER-FORMING ACRYLONITRILE POLYMER CONTAINING, IN THE POLYMER MOLECULE,AT LEAST 65% OF ACRYLONITRILE IN DIMETHYL FORMAMIDE WHICH COMPRISESSPINNING THE SOLUTIONS INTO A COAGULATING BATH CONSISTING ESSENTIALLY OFA MIXTURE OF WATER AND FROM 35 TO 80% BY VOLUME OF DIMETHYL FORMAMIDE,WITHDRAWING THE YARN THUS FORMED FROM THE BATH, AND STRETCHING THE YARNBY 200 TO 300% OF ITS LENGTH, THE COMPOSITION OF THE COAGULATING BATHBEING MAINTAINED SUBSTANTIALLY CONSTANT FROM THE BEGINING TO THE END OFTHE SPINNING OPERATION.